In some conventional ethylene oxide plants, the aqueous quench bleed from the quench section of the ethylene oxide absorber is sent directly to a disposal well. The quench bleed contains a low concentration of ethylene oxide. Ethylene oxide (EO) has been shown to be mutagenic to test animals and is a "suspected carcinogen." EO in pure form has a very low flash point and is highly flammable. The Threshold Limit Value (TLV) for EO based on the standards set by the American Conference of Governmental Industrial Hygienists is 1 ppm in air. To avoid the contamination of water supply with EO, the Environmental Protection Agency has ordered that the disposal of the ethylene oxide to the well be discontinued. A method for removal of ethylene oxide from the aqueous quench bleed is therefore definitely needed.
One method for accomplishing such ethylene oxide removal has been discussed in U.S. Pat. No. 4,427,507, issued Jan. 24, 1984, which teaches a process for separating glycols from an electrolyte-containing aqueous solution which can be a quench bleed from an ethylene oxide plant. The process comprises electrolyzing said solution to increase the glycol to electrolyte content and subsequently removing a substantial part of the water. Ethylene oxide is removed by distillation.
It is an object of the present invention to provide a process enabling the conversion of a low concentration of ethylene oxide in a salt-containing aqueous quench bleed to glycols which are considered much less toxic than EO. Glycols, in general, have much higher flash points and are not flammable. The glycols produced can be recovered. In a typical ethylene oxide plant, as much as 24,000 lbs. of glycols per day can be recovered from the quench bleed which amounts to about six thousand dollars worth of glycols products.
A further object of the invention is the provision of an improved process enabling the efficient recovery of a low concentration of ethylene glycol from a salt-containing aqueous solution.
Still another object of the invention is to provide a process for the recovery of glycols from the bottoms stream of the glycol bleed flasher in an ethylene glycol plant. The glycols from the bottoms stream of the glycol bleed flasher are normally disposed as a waste stream in a conventional plant. The overall yield of the EO/EG process is increased using this process contemplated by the present invention.
Other objects and advantages of the present invention will become apparent from the following detailed description thereof, made with reference to the attached drawing wherein the single FIGURE represents one form of apparatus capable of being used in carrying out the process of the invention.